Automatic threading apparatus for lathes



Sept. 15, 1959 D, E. MACKENZIE 2,903,933

AUTOMATIC THREADING APPARATUS FOR LATHES 7 Filed Jan. 20, 1955 6 Sheets-Sheet 1 INVENTOR.

BY wwp 1959 D. E. MACKENZIE 2,903,933

AUTOMATIC THREADING APPARATUS FOR LATHES Filed Jan. 20, 1955 6 Sheets-Sheet 2 f V A Dona/a E. Mac/renz/e INVENTOR.

BY fie f. m

.K/QWWL ATTOR/VEKS Sept. 15, 1959 D. E. MACKENZIE 7 3 AUTOMATIC THREADING APPARATUS FOR LATHES Filed Jan. 20, 1955 6 Sheets-Sheet 5 Dona/a Mackenz/e INVENTOR.

Sept. 15, 1959 D. E. MACKENZIE Filed Jan. 20, 1955 6 Sheets-Sheet 5 .llllm INVENTOR. BY WWMQ AUTOMATIC THREADING APPARATUS FOR LATHES 'Sept. 15, 1959 D. E. MACKENZIE AUTOMATIC THREADING APPARATUS FOR LATHES 6 Sheets-Sheet 6 Filed Jan. 20, 1955 fla/vo/o E Mackenz/e IN VEN TOR. M

United States Patent *Ofiice 7 2,903,333 Patented Sept. .15, 1959 AUTGMATIC THREADING APPARATUS 'FOR LATHES Donald E. Mackenzie, Houston, Tex.

Application January 20, 1955, Serial No. 483,145

3 Claims. (CL '82-5) This invention relates to new and useful improvements in .automatic threading apparatus for lathes.

.One object of .the invention is to provide an improved threading apparatus in the form of an attachment for automatically controlling the threading operation, said apparatus being adaptable for use with any type of turning machine having a cross slide and a lead screw, but being particularly applicable to engine and turret lathes.

Animportant object of the invention is to provide an improved threading apparatus for lathes which willefiiciently and automatically control all of the operations involved in threading a work piece, whereby the apparatus not only relieves the operator but also speeds up the threading operation and in addition assures more accurate threading.

Another object is to provide an apparatus of the character described which will automatically control the threading of a work piece by the single point threadcutting method, said apparatus controlling the depth of the cut, the length of travel of the cutting tool, the return of the carriage after each pass of the tool and also the number of passes or cuts which may be required to produce a proper thread.

Still another object is to provide an apparatus of the character described which controls all of the operations involved in single ,point thread cutting and which may be employed for cutting straight threads, either internal or external, or which may be used with the usual taper attachment whereby tapered threads may be cut.

A particular object is to provide an apparatus of the character described wherein the various elements thereof are automatically operated, either hydraulically, pneumatically or electrically, or by a combination of such power sources; the apparatus being arranged so that operation may be commenced by manual control of the operator and thereafter said apparatus will complete the entire threading operation automatically and without any further manual control by the operator.

A further object is to provide an apparatus of the character described, which is in the form of an attachment and which may be readily and easily applied to any standard type of lathe and withoutany change in said lathe.

Still another object is to provide an improved apparatus which includes a power operated unit for controlling the movement of the cutting tool in a direction which determines the depth of the out, said unit including a simplified means for effecting proper inward movement of the cutting .tool as the threading operation progresses;

A still further object is to provide an improved control system which combines hydraulic power with electrical control for actuating the apparatus.

The construction designed to carry out the invention will be hereinafter described, together with other features thereof. a

The invention will be more readily understood from a reading of the following specification and by reference "to the accompanying drawings forming a part thereof,

'2 wherein an example of the invention is shown, and wherein:

Figure 1 'is a plan view of a lathe in schematic illustration, showing an automatic threading attachment, constructed in accordance with the invention, applied thereto;

Figure 2 is a transverse, vertical sectional view taken on the line 22 of Figure 1;

Figure 3 is an isometric view of the control unit for controlling the movement of the cross slide;

Figure 4 is a longitudinal sectional view ofthe operating unit illustrated in Figure 3;

Figure 5 is a transverse sectional view taken on'the line 55 of Figure 4;

Figure 6 is a side elevation of the control unit shown in Figures 3 to 5;

Figure 7 isa partial isometric view of the unit shown in Figure 3 with portions thereof broken away; 3

"Figure 8 is an isometric view of the control assembly for the half nut 'or connecting element which is adapted 'tojbe connected with the lead screw of the lathe;

Figure 9 is a side elevation of said control assembly and connecting nut;

Figure 10 is a plan view thereof;

Figure 11 is a detailed View showing the adjustable operating rod which actuates one of the limit switches;

Figure 12 is an elevation of the return cylinder assembly which returns the carriage to starting position; and

Figure 13 is a diagrammatic view illustrating the hydraulic system and including a wiring diagram of the electrical control means for controlling the operation of said system.

In the drawings, the numeral 10 designates a lathe which may be of any suitable construction. As shown in Figures 1 and 2 the lathe includes the usual base 11 having a bed provided with longitudinal ways :12 upon which are slidable theusual carriage .13. As is well known, the carriage 13 is adapted to be moved longitudinally along the ways by the usual longitudinal extending lead screwl l. Connection between the carriage and the lead screw is made by means of a connecting element 15, which is generally referred to as a half nut. By selectively engaging or disengaging the half nut 15 with the lead screw 14 the carriage is selectively 'connected to or disconnected from said lead screw; when connected to the lead screw operation of the screw will move the carriage longitudinally along the bed or ways 12 of the lathe.

Mounted upon the carriage 13 is the usual cross slide 16 which is adapted to be moved transversely of the carriage by means of the usual traverse screw 17 and a tool carrier 18, within which a cutting tool 19 is mounted, is secured to the cross slide 16. The cutting tool 19 is adjusted relative to the work piece W, which is shown in dotted lines in Figure 1, by adjusting the cross slide transversely-of the bed of the lathe. By connecting the carriage 13 to the lead screw 14, the cutting tool is caused totravel longitudinally with respect to the work piece which is held in place by the usual chuck 20.

When a threading operation is being carried out, it is normally necessary for the operator to manually adjust the cutting tool 19 to the proper depth which will'be re quiredfor the first cut or pass and-then the operator manually controls the longitudinal movement-of the carriage and cutting tool throughout the length of the thread which it is desired to cut. In most instances in single point threading, several .passes or cuts are required and thus the attention of the operator is required throughout the threading operation. The purpose of the present invention is to provide in the form of an attachment a means for automatically controlling the various factors which are involved in forming or cutting the complete threads.

In carrying out the present invention, a cross slide control unit 21 which includes a cylinder and piston A is connected with the cross slide 13 and is adapted to control the transverse position of said slide to control the position of the cutting tool 19 with respect to the work piece W. A control assembly generally indicated by the numeral 22 and including a piston and cylinder B is associated with the half nut 15 which is adapted to connect with the lead screw 14 and this assembly, as will be explained, controls the connection of the half nut 15 with said lead screw to efiect operation of the carriage by said lead screw. A return cylinder assembly 23 which includes a cylinder and piston C is provided for the purpose of returning the carriage to its initial or starting position with respect to the work piece W. The pistons A, B and C are operated in proper sequence to control the threading operation and may be hydraulically or pneumatically actuated. Operation of the pistons A, B and C is controlled by means of suitable electrical controls which include a limit switch Sl which is located at the starting position of the carriage; a second switch S2 which is located at the terminal position of the carriage and which controls the return of said carriage; and a third or shut-off switch S 3 which functions to halt operation of the apparatus after completion of the threading operation.

When the carriage is in a starting position with the tool 19 retracted from the work piece, said carriage will be in a position adjacent to the limit switch 8-1 in Figure 1. Upon closing of a master start switch 8-4, the apparatus is caused to operate in the desired sequence to carry out threading of the work piece W.

In such sequence, the limit switch S1 first causes the piston A to operate to move the cutting tool 19 into engagement with the work piece and thereafter, the piston B is operated to engage the half nut or connecting element 15 with the lead screw 14, whereby the carriage is caused to travel longitudinally of the lathe in a direction to the left in Figure 1. As the cutting tool 19 completes its first pass over the work piece the carriage contacts the limit switch S2 and simultaneously therewith a mechanical release, which is generally indicated at 24 in Figure l, is actuated. The mechanical release 24 disengages the half nut or connecting element 15 from the lead screw 14, whereby further longitudinal movement of the carriage 13 in a direction to the left in Figure 1 is halted. The engagement of the limit switch S2 functions to first actuate piston A to retract the cutting tool 19 from the work and to thereafter operate the piston C in the return cylinder assembly 23, whereby the piston rod 25 on the piston C is engaged with the carriage and moves said carriage longitudinally to the right in Figure 1, until said carriage is returned to its initial or starting position. As the carriage moves back to starting position a switch operating member 26 which is secured to the carriage again engages the limit switch Sl to actuate this switch and effect a repetition of the cycle of operations. Upon this second cycle, the cutting tool 19 is moved inwardly an additional distance, the carriage is caused to traverse the work piece, is then halted and returned to starting position for the subsequent cycle of operation. The apparatus may be adjusted, as will hereinafter appear, to control the depth of each cut or pass of the cutting tool and to control the number of such cuts or passes. When the threading operation is complete, the shut-off switch 8-3 is actuated to halt further operation of the apparatus. It is thus obvious that the apparatus automatically controls the various operations involved in the threading of the work piece and after the operator once starts the apparatus by means of the start switch S4, no further manual control is required. The depth of the cut, the length of each cut or pass and the, number of such cuts or passes is automatically controlled until the threading is complete. The results are accomplished by properly actuating the control pistons A, B and C in the proper sequence.

The cross slide control unit 21 is clearly shown in Fig- 4 ures 3 to 7 and includes an outer support or casing 27 which is suitably secured to the carriage 13 of the lathe (Figure 4). The upper portion of the support 27 is formed with a bore 23 which is in alignment with the cross slide traverse screw 17, which screw controls the position of the cross slide 16. A nut or colltar 29 is mounted upon the threads of extended end of the screw 17 and has its lower portion extending downwardly through a slot 30 formed in that portion of casing 27 which is below the bore 28. Guide sleeves 29A and 29B may be formed on the nut 29 and said sleeves surround the screw on each side of said nut. A recess 31 is formed in the lower portion of the casing or housing and this recess has longitudinal guide grooves 32 (Figure 3) in its walls which are engaged by ribs 33a extending outwardly from a slide block 33, whereby said block is slidable within the recess 31. The upper inner end of the block is connected by a suitable pin 34 with the nut 29, and it is obvious that when the slide block 33 is moved within its recess a similar motion is imparted to the traverse screw 17 of the cross slide to impart transverse movement to said cross slide with respect to the bed of. the lathe. Since the cutting tool 19 is carried by the cross slide, it will be evident that an adjustment of said cross slide will result in an adjustment of the tool with respect to the work piece W which is held within the lathe. The slide block 33 is suitably connected to the piston rod 34 of the piston A and when said piston A is moved Within its cylinder the slide block will be moved to adjust the cross slide.

For limiting the outward movement of the slide block 33 in order to control the depth of the cut to be made by the tool 19, a cam shaft 35 extends transversely through an opening 36 in the slide block and also through openings in the side walls of the support or casing 27. This cam shaft is suitably journaled in the walls of the support and has a plurality of bottom cams 37 which are mounted on the exterior of the shaft, being disposed within the recess 36 of the slide block. The button cams 37 are each of a different thickness or radial projection so that each projects a different distance outwardly from the surface of the cam shaft, as is clearly shown in Figure 4. Each button cam is adapted to coact with a stop 38 which is located within the slide block 33 and it will be evident that when the piston A is operated to move the slide block outwardly or in a direction to the left in Figure 4, the stop 38 of said slide block will engage the particular button cam 37 which is aligned therewith and this will limit the movement of the slide block in such outward direction. Movement of the block in this direction will control the depth of the cut to be made by the cutting tool 19 and by selectively locating the cam buttons of different radial projections in alignment with the stop 38, the movement of slide block 33 and therefore the movement of the cutting tool will be accurately controlled.

In performing the threading operation, it is desirable to intermittently increase the depth of the cut upon each successive pass of the tool and thus, the movement of the slide block should be gradually increased in successive steps. For this purpose, the button cams are arranged so that at the start of the threading operation the button cam of greatest radial projection will be engaged by the stop 33 and thereafter the button cams of successively smaller radial projection will be moved into alignment with the stop 38 until the threading operation is complete.

For indexing the button cams 37, one end of the cam shaft 35 is extended and has a ratchet 39 secured thereto. This ratchet is adapted to be engaged by an operating pawl 40 which is carried by a plunger 41 mounted in a suitable supporting frame 42. When the plunger 41 is moved against the tension of a coiled spring 41a the pawl 40 will engage one tooth of the ratchet and will impart a rotat on to the shaft. The teeth of the ratchet 39 are of course correlated with the button cams so that each t me thatithe'zplung'er "i1 actuated ililififIZOtfltiGllaBF-thfi sh-aft will thernext successive cam'with ItIIBTSfQP-BS. EFhe rplungerd-l. #which :actuates "the-indexing ratchet 39 is op- .erated by an 1 angular arm 43 which Ehas its lower :end seacured :to the undersideuof theslide block 135, .as shown in Figure 5. Thus when ther'slide' block is=moved=inwardly after the completion of each cut or pass-f ithe :cutting .todl'r19, the :a'rm43 iunctions :to =ro'tate -the-ratchet39 and :move the tnext' successi-ve :buttonacam *into position in alignment with thezstop 38; upon return of the slide block ital-its outermost position, :the nexncam it-hus controls the amount of outward movement f the :slide :block and thereby controls .theidepthzof thecut. 4

.nnay hezdesirable :in cer'tam'instances'to manually actuate the sindexingzratchetaw :and :for this purpose a second plunger 44 is provided. This plunger has a pawl 145 adapted. tozengageithe ratchet teeth in the same manmer as athe;pawl 4.0. .An'operatinglever '46 coacts with sthe :plunger 44 :and this lever :may be connected to a z-snitaible rod 47 with in manual COI1tI'01lIl'I0lll1-t6d on the lathe. "Under mormal operation the indexing ratchet 39 is automatically actuated by the sliding movement et the :slide FblDCk 33,1but when desired may be manually eacz-ated throughzlever 46.

EIlhe cam shaft 55 'haslits oppositeend formed with a plurality iof recesses =48 :(Figure 5') which co'act 'wvitha ispring-apressed detent 49 whereby' the camshaft is docked in reach indexed :position by the friction of decent to prevent an unintentional'irotation of :said shaft; The outer extended end .of "the shaft is formed with-a collar 50 having asingle groove 51 which 'is 50 located with refPCt t0Wh6 bl1tt0n cams that said gro'ovebecomes aligned with an :operating member '52 of the control switch tS-3 wvhen the rthreadingxiperation is complete. 1Thus atter threading lot the work piece has been completed, -the [groove '51 on ithe collar :50 moves opposite the switch :actuatin'g element 52 and operates 'the shut-off =switch 5-3 to cut ofi further operationsof'the apparatus.

control assembly for controlling the engagement and disengagement :of the half nut or connectingelement -1'5.is -clea1ly.shown in Figures 8 to 10. As illustrated the half nnt or connecting element comprises a pair of pivoted elements '53 having internally threaded jaws '54 which are adapted to close about and engage the lead screw '14 of the lath e. The handles 55 oi thee'lements extend outwardly beyond the pivot point "56 and a co'iledspring '57 mormally urges the handles to a position which disengages the clutch jaws 54 'fromthe lead screw 14. For engaging the jaws of the element 15 with the'lead-screw, a pairof toggle links 58 are pivoted to the handles 55 and to each other. An operating rod "59 extends from the center' connection between :the toggle links and has its opposite end connected to an actuating arm I 60 which is :mounted upon a'shaft 61. The sha'ft 6-1 is adapted to he rotated by means of a ring 62 which abuts a' flange E63 mounted on the *shaft'61 andconnection between the flange and ring is made through screws 64 which project outwardly from said llange and engage within arcu'ate slots 65 in said ring. The piston 33 which has its cylinder'66a connected to the carriage 13 01": the lathe has its piston rod 66 connected at '167 with the r-ing '62 and when the piston -B is actuated, the ring 62 rotates whereby one end of each slot 65 engages the pin 64 Within-said slot to impart a rotation to the shaft 6 1; such rotation is in a direction which will "break the toggle links 58 and cause the threaded jaws 54 of element 15 to be engaged with the lead screw "1-4 of thelathe. Engagement'of'the jaws with the "lead screw is maintainedby means of a springpres'sed locking detent 68 which is carried 'by 6811 mountedon the shaft 61. The locking detent-engages a recess 69 in a *bracket '70 which is carried by the carriage 'Thus when the piston B has rotated the shaft to engage the element 15 with the lead screw, such element 'is locked against 'diseng-a'gement from the lead screw until the locking detent '68 has been depressed. Therefore, *the 7,6 :piston B may-return to its initia1 position, such movements .zbeing @permitted by the arcuate slots "65, without disengaging the ;jaws54 of the half nut from connection =witl1 =the leadscrew.

The half :nut or 7 connecting element 15 remains engaged with thedead screw until a release :lever 71 which coacts witha plunger 72 is actuated by'a :rod 73. The rod 13a is carriedby the lathe and is positioned "at-a point adjacent theiemd 0f the travel of the carriage, the mechanical release assembly being generally'indicatedat 24 in Figure 1. As the-carriage reaches the endofits travel, the lever 71 is engaged'by the rod 73'whichdepresses the plunger 72 and disengages the detent 68 'from its "recess :69; when occurs the spring '57 whichiis constantly "urging the half not or connecting element "toward disengaged position functions to release the jaws "54 from'the dead screw. It is 'thus evident that with the arrangement shown -the harm or connecting element '15 is engaged with the lead :sc'rew by operation 0f the :p'iston 'B and d-iseng'agedl-from said lead screw after the travel of the "carriage has been completed *by the mechanical =release assembly 24 which' comprises 'the detent, plunger-rod 72 and associated parts. i

'As has been mentioned, 'the carriage {[3 is r-et'urned to its starting position by the return cylinder assembly 23. This as'sembl-y (Figure 1 2) is a simple cylinder having :the piston- C therein and said piston has-a rod25 which extends outwardly for engagement with the carriage 13 Thedi'mitswitcihS-Z is adapted to be -engaged by thecarriage 13 when'smd caniage reaches the limits of its travel and upon operation of limit switch 8-2 the pisto'n C is actuated to m'ove its piston-rod in adirecition to the right in Figure 1. The piston rod engages the carriage and moves said carriage back to its initiafl or starting posi- -ti'on. As the carriage returns to starting position the switch actuating element '26, which is more clear-1y illustrated in Figure '11, engages a rol1er80to dep'res's anal-m '81 and thereby actuate the 'limit switch 8-1. It is noted that the element '26 may 'be constructed ot telescoping members which maybe moved to various relative' positions and locked therein by a set screw 82 tdvary the over-all length of said element.

Any suitable system of control may be employed for controlling the operation of' the pistons A, B 'and'C in a desired se'quence, but in Figure l3 a preferred form of control means -is schematically illustrated. As shown in "this'figure the piston Ahas a crossover"vajlve 8'5 associated therewith, which valve is actuated by an electrical solenoid A-1. Piston "B has asimilarcross-over valve 86, 'whichis actuated by a solenoid B 1, 'whilecylinder C has associated therewith a-cross-over valve 87 controlled-by a solenoid C1. A sequence valve 88j'is' disposedin the hydraulic system -between the piston A and the piston B, and as is well known, type ofvalve permits operation of piston A and prevents operation of piston B until a predetermined pressure has built up in the cylinder of pistom said valve thus "functions to cause operation of piston A first after which ipiston B maybe actuated. sequence valve 89 'is also connected in t'he circuit in association with piston C and is arranged so thatpiston A will operate p'rior'to the'time thatpiston-C operates.

A relay A-2 is associated with'the operating solenoid A-l of piston A and is provided for the purpose of holding the solenoid A4 in closed position after the same has been initially energized, as will be hereinafter explained. The limit switch S 1 is connected to the sole"- noids .A- -1 and B 1 50 that when the switch is actuated the solenoids A -1 and -B'-1 are operated to cause an op eration of'pistons A and B. Since switch 8-1 is the switch at the beginning of the operation, piston A is operated to adjust the cutting tool after which piston B is operated to engage the half nut or connecting element 15 with the 'lea'dscrew 14. At this time the other limit switch S4 is open and pistonC which the return piston is inactive.

' After pistons A and B have been actuated the carriage begins to move to the left and this opens limit switch S 1. However, because of the relay A-2, piston A maintains the cutting tool 19 in contact with the work but piston B may return to its initial position because solenoid B1, being de-energized, will actuate valve 86 to reverse the direction of pressure upon this piston. As noted inconnection with'Figure 8, piston B can return to its original position without disengaging the half nut 15.

As the carriage 13 completes its movement, the half nut is released by reason of the release assembly 24, the release lever 71 being engaged by rod 73 (Figure 8), and thus further movement of the carriage is halted. Simultaneously with the disengagement of the half nut from the lead screw, the carriage strikes the limit switch -2 to close said switch. When this occurs the relay A-2 is released and the solenoid C-1 is energized. Because of the sequence valve 89, piston A first returns to its initial position to withdraw the tool 19 from the work, after which piston C is actuated to return the carriage 13 to starting position. When the carriage returns to starting position the switch 8-1 is again actuated to repeat the operation. It is noted that at the time that piston A is moved to move slide block 33 and thereby retract the tool 19 from the work, the indexing ratchet 39 is operated to move the next button cam 37 on the cam shaft 35 into position to control the limit of movement of the cutting tool relative to the work upon the next operation of slide block 33. The foregoing cycle of operations is continued successively until the threading operation is complete.

The overalloperation of the apparatus is believed to be obvious. Initially the carriage 13 is in starting position adjacent the switch S1 in Figure 1. The operator actuates the master switch S-4, and upon such operation piston A moves the tool into position with the work piece. The half nut or connecting element 15 is then engaged with the lead screw and the carriage and tool traverse the work piece for the desired length. Upon reaching the end of its travel the mechanical release mechanism 24 disengages the half nut while the switch 84. functions to retract the piston A and move the cutting tool away from the work and to thereafter operate cylinder C to return carriage to starting position. Upon return to starting position the carriage actuates the switch S1 through the rod 26, and this causes piston A to again move the tool into contact with the work. Since the button cams have indexed during the retraction of piston A, the tool will now move into engagement with the work to a deeper depth so that the next cut will be made. Thereafter the cycle of operation is repeated until the desired number of cuts to complete the threading operation have been made.

The apparatus is relatively simple in construction and may be mounted on the lathe without any material change in the lathe structure itself. It is thus in the form of an attachment and is applicable to any type of turning machine having a carriage and a lead screw; actually it has been found to be adaptable to both engine and turret lathes. Not only does the apparatus relieve the operator of the manual control of the depth of cut and the length of travel, but it also provides for a faster operation and more accurate threading. It is of course evident that the button cams 37, which are mounted on the cam shaft 35 may be varied in thickness and in number in order to meet the particular needs of the work being done; also, any suitable cam projections could be employed upon the shaft. Although control of the pistons A, B and C has been described as being a combination of hydraulic power and electrical control, it is evident that the pistons may be actuated pneumatically and other methods of automatic control may be employed. So long as the various operations which are performed in the threading of a pieceof material are automatically controlled, the purposes of the invention will be accomplished.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention. 1

What I claim is:

1. A turning machine for cutting threads comprising, a base having ways thereon, a carriage slidable along the ways, a rotatable chuck on the base for supporting a work piece, a lead screw mounted on the base, a half nut mounted on the carriage and connectable with the lead screw to move the carriage along the ways with rotation of the lead screw, a first closed cylinder and piston therein mounted on the carriage, a lost motion connection between the half nut and one of said cylinder and piston including a pin and shoulder which are engaged by pressurizing the cylinder and move the half nut into engagement with the lead screw, a detent holding the half nut in engaged position during each cut, said lost motion connection permitting retraction of said first piston and cylinder after the detent is engaged without releasing the half nut, a detent release carried by the base and engaging and releasing the detent at the end of each cut, a spring urging the half nut toward disengaged position and effective upon release of the detent to return the half nut to disengaged position, a cross slide mounted on the carriage for movement transverse to said movement of the carriage and carrying a cutting tool, a transverse screw mounted on the carriage and controlling movement of the cross slide, a nut slidably carried by the carriage and threaded on the transverse screw, a stop carried by the nut, a cam mounted on the carriage and engaged by said stop as the cutting tool is moved into cutting position to determine the depth of each cut, means for indexing said cam in response to each reciprocation of said nut, a second closed cylinder and piston therein mounted on the carriage and connected to the nut for reciprocating the nut and for holding the stop against the cam during each cut, a third closed cylinder and piston therein mounted on the base for engaging and returning the carriage to starting position at the end of each cut, and a hydraulic control system including a source of liquid under pressure connected to each of said first, second and third cylinders through first, second and third control valves, respectively, said first and second valves operable in response to movement of the carriage to a position to begin a cut to pressurize one side of said first and second pistons and move the half nut into engagement with the lead screw and the stop into engagement with the cam to position the cutting tool in cutting position, said first valve reversing flow of pressure fluid to said first cylinder to pressurize the other side of said first piston to withdraw the pin from the shoulder of said lost motion connection in response to movement of the carriage by said lead screw, said second valve reversing in response to the carriage reaching the end of a cut to reverse fiow of pressure fluid to said second cylinder to pressurize the other side of said second piston and withdraw the cutting tool, said third valve operable in response to the carriage reaching the end of a cut to pressurize the third cylinder and return the carriage to beginning position.

2. As a subcombination a cross-slide control adapted to be secured to a turning machine carriage and to reciprocate the transverse screw of the cross-slide comprising, a support adapted to be mounted on a turning machine carriage, a cam mounted on the support, a nut slidably carried by the support and adapted to be threadedly connected to the transverse screw of the cross-slide, means for indexing the cam with each reciprocation of the nut relative to the support, a stop carried by said nut and engaging the cam upon reciprocation of the nut in one direction, and means including hydraulic operator for selectively reciprocating and holding the stop in engagement and in disengagement with the cam, respectively.

3. As a subcombination, means for releasably securing a carriage to the lead screw of a turning machine comprising, a half nut having both halves pivoted on a car riage at a common point, handles on each half of the nut, a spring between said handles urging the two halves of the half nut toward closed position, an operating rod attached to each handle and movable to a first position to close the half nut and to a second position to permit the spring to open the half nut, a closed cylinder having a piston therein mounted on the carriage, a lost motion connection between the rod and one of the piston and cylinder including a shoulder and pin engageable upon pressurizing the cylinder and moving the operating rod to nut-closing position, said lost motion connection permitting reverse relative movement of said piston and cylinder to disengage the shoulder and pin Without opening 10 the half nut, a detent releasably holding the half nut in closed position upon movement of the rod to nut-closing position, and means for selectively reciprocating said piston and cylinder relative to each other.

References Cited in the file of this patent UNITED STATES PATENTS 

